C++ addition precision

example.cpp

#include <iostream>
#include <iomanip>

using namespace std;

int main () {
   double a = 0.1;
   double b = 0.2;
   double result = a + b;

   // prints 0.30000000000000004441
   cout << setprecision(20) << result << endl;

  return 0;
}